Convergence cup with one-piece shield

ABSTRACT

A convergence cup for use in color kinescopes includes an improved shield structure for magnetically separating the pairs of pole pieces. The one-piece shield is formed from a single metal strip with tabs at its ends by bending it 180* along a lateral line and cutting from the strip a third tab extending from the bend line, and bending the resulting legs 120* outwardly along central lateral lines to form a Y-shaped shield. The onepiece shield is then secured in position inside the cup by spot welding the tabs to the cup wall.

United States Patent 1 Rimmler 1 Jan. 9, 1973 [54] CONVERGENCE CUP WITHONE- PIECE SHIELD [75] Inventor:

[73] Assignee: The Stanley Works, New Britain,

Conn.

22 Filed: Dec. 30, 1970 [2]] Appl. No.: 102,764

52 us. (:1... ..313/77,313/79 51 int. Cl .1101; 29/08, H01 j 29/02, H01j 3 1/20 58 Field ofSearch ..313/77, 70 c, 69 c, 79

[56] References Cited UNITED STATES PATENTS 3,324,323 6/1967 Burdick m1..313 70cx 3,440,468 4/1969 Suzuki et al. ..3l3/77 X Fred F. Rimmler,Manhasset, N.Y.

[2/1970 McQueen et al. ..3l3/77 9/1971 Tsuneta et al. ..3l3/70 C PrimaryExaminer-Robert Segal Attorney-Brumbaugh, Graves, Donohue & Raymond [57]ABSTRACT A convergence cup for use in color kinescopes includes animproved shield structure for magnetically separating the pairs of polepieces. The one-piece shield is formed from a single metal strip withtabs at its ends by bending it 180 along a lateral line and cutting fromthe strip a third tab extending from the bend line, and bending theresulting legs 120 outwardly along central lateral lines to form aY-shaped shield. The one-piece shield is then secured in position insidethe cup by spot welding the tabs to the cup wall.

2 Claims, 5 Drawing Figures PAIENTEDJAH' 9 I975 3.7 l O. 164

HIE

' BY v W MIDM -I- M his CONVERGENCE CUP WITH ONE-PIECE SHIELD BACKGROUNDOF THE INVENTION This invention relates to convergence cups'for colorkinescopes and, in particular, to an improved magnetic shield for use insuch convergence cups and the method of forming the cup.

The most common type of color kinescope (color television picture tube)includes three electron guns that direct parallel electron beams in thedirection of the screen. The beams are directed through a mask, having adense array of openings, to a phospher dot pattern on the face of thescreen. The originally parallel beams produced by the electron guns mustbe deflected so that they converge towards each other and meet at theopenings in the mask. Structure in the kinescope for causing convergenceof the electron beams includes an assembly, commonly referred to as aconvergence cup, mounted in the neck of the tube in front of theelectron guns. The convergence cup includes three pairs of magneticpoles, one pair for each electron beam, which form parts of magneticcircuits for establishing magnetic fields through which the electronbeams pass and by which they are deflected to converge at the mask.

The convergence cup must be manufactured from high grade materials torelatively high tolerances, if it is to operate properly, particularlyin view of the fact that color kinescopes are mass produced. Hence thespecific structure of the cup and various manufacturing operations usedto make the cup are of importance in meeting the tolerance requirements.

One form of convergence cup that has been widely manufactured and usedcomprises a cup-like body having a circular base and a cylindricalflange extending perpendicularly from the perimeter of the base. Thebase has punched openings through which the electron beams will pass,and the flange has openings to provide for the installation of the polepieces and an internal shield which magnetically separates the pairs ofpole pieces.

Various forms of magnetic shields have been used but all have in commontheir fabrication from more than one metal strip. The most widely usedmagnetic shield structure includes three strips bent 120 intermediatetheir ends and inserted in the cup to form a Y- shaped shield. Thisresults in extra manufacturing operations, including extra spot welds,and the use of sizable quantities of the magnetic metal, a disadvantagein view of the cost of the high nickel content metal.

SUMMARY OF THE INVENTION In accordance with the present invention, anovel and improved convergence cup is provided through use of aone-piece Y-shaped shield that affords many advantages over previousconvergence cups. In particular, the inventive convergence cup comprisesa cup-like body having a circular base and cylindrical flange extendingfrom the perimeter of the base. As with previous forms of convergencecups, the flange is formed with elongated openings aligned with itsaxis, one opening for each of the six poles that make up the three .polepairs. The pole pieces are generally L-shaped members formed of magneticmaterial with their longer portions constituting the pole portion andextending generally radially inwardly from the flange. The shorter legof the L abuts the external surface of the flange and is attachedthereto such as by spot welding.

The magnetic shield structure of the convergence cup, which provides thesubstantial advantages of the invention, comprises a single metal stripbent to form a one-piece Y-shaped shield that magnetically separates thepairs of pole pieces. More specifically, the Y- shaped shield is formedfrom a single strip of metal by the method of bending the strip 180along a lateral line intermediate its ends and then bending the tworesulting legs outwardly along lateral lines intermediate their ends. Tofasten the Y-shaped shield to the flange, two tabs extending from theends of the strip and a third tab cut from the strip and extending fromthe bend are provided, such tabs being oriented to extendcircumferentially of the cylindrical flange. In one embodiment of theinvention, the tabs extend through three slots in the cylindrical flangeand are attached by spot welding to the external surface of the flange.

In another embodiment of the invention, the Y- shaped shield is fastenedin position by welding the tabs to the interior surface of the flange.

DESCRIPTION OF THE DRAWINGS The foregoing and further advantages of theinvention will be more readily understood when the following descriptionis read in connection with the accompanying drawings, in which:

FIG. 1 is a plan view of a convergence cup formed in accordance with thepresent invention;

FIG. 2 is an elevation of the convergence cup of FIG.

FIG. 3 shows a single metal strip from which is formed the one-pieceY-shaped shield shown in FIG. 1;

FIG. 4 shows a modified embodiment of the inventive convergence cup; and

FIG. 5 is an elevation of the convergence cup of FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1to 3, which show a typical embodiment of the invention, the convergencecup includes a cup-like body 10 formed by a circular base 11 and acylindrical flange 12 extending perpendicularly from the perimeter ofthe base. Preferably the base and flange are integral parts of aone-piece drawn cup of a non-magnetic material.

Three circular apertures 13 in the base 11 are located 120 apart andequidistant from its axis. The apertures 13 pass electron beams fromthree electron guns of a color kinescope through the convergence cupand, in addition, receive circular flanges associated with the gunassembly to attach it physically to the convergence cup. The base 11 isalso formed with six circumferentially spaced-apart bosses 14 thatproject from its bottom surface and serve as spacers to orient theconvergence cup with respect to the other elements of the electron gunassembly.

The cylindrical flange 12 is formed with three circumferentiallyspaced-apart pairs of openings 15. Each opening 15 is substantiallyrectangular and oriented with its longer axis aligned with the axis ofthe flange 12. Preferably the openings '15 are each formed by cuttingalong one long edge and the two ends of the potential opening, and thenbending inwardly the resulting rectangular piece to provide an inturnedrib 16 extending along the other longer edge of the opening 15. Eachpair of openings receives a pair of pole pieces 17, and the ribs 16 arecut and bent so that they extend along adjacent edges of juxtaposedopenings. The openings are substantially wider than the thickness of thepole pieces to facilitate both the forming of the openings and theinsertion of the pole pieces during assembly. Note that the ribsstrengthen the relatively thin wall of the flange and make it lesslikely that distortion will occur during handling and manufacturing ofthe cup.

The L-shaped pole pieces 17, having longer and shorter legs 17a and 17b,respectively, and formed of a magnetic material, extend generallyradially inwardly through the flange. A bend is formed at each free endof the leg 17a to provide a desired flux distribution between adjacentpole pieces.

The shorter leg 17b of each pole piece bears against the outer surfaceof the flange l2, and for each pair of poles, extends in a directionaway from the other pole. ln assembling the convergence cup, each polepiece 17 is inserted into one of the openings and positioned so that thelonger leg 17a abuts the rib 16 of that opening. Each pole piece is thensecured in position and spot welded at welds 18 to attach the leg 17b tothe flange.

In accordance with the present invention, a novelone-piece Y-shapedmagnetic shield is used to divide the volume within the cylindricalflange 12 into three magnetically shielded sections with one of thepairs of pole pieces 17 in each section. In particular, as shown in FIG.3, a flat metal strip 20 is formed with tabs 21 extending from its endsat its upper edge. A lateral bend line 22a intermediate the strip endsfunctions to divide the strip into two legs.

In the novel method of manufacturing the Y-shaped shield 19, the strip20 is bent l80 along the bend line 22a to form shield sections 22 and,at the same time, a further tab 23, indicated by dashed lines 24, is cutfrom the strip 20. At, the same time or subsequently, 120 bends alonglateral bend lines 25a are made to form shield sections 25 and the tabs21 and 23 are bent slightly more than 90, as shown in FIG. 1, to extendcircumferentially of the flange 12 when the shield 19 is inserted intothe cup. 7

To assemble the convergence cup with the Y-shaped shield 19 positionedinside the cylindrical flange 12, thereby magnetically shielding thepairs of pole pieces 17, the shield is inserted in the cup with the tabs21 and 23 extending through openings 26 in the flange 12. The

circumferentially extending tabs 21 and 23 are then spot welded by welds27 to the flange 12 to complete the convergence cup.

With the inventive one-piece shield, a saving of more than one-third ofthe relatively expensive magnetic material (on the orderof 50 percentnickel content ordinarily is required in the shield material) used inthe conventional three-piece shield is achieved. Moreover, even if atwo-piece shield were to be used, the inventive Y-shaped shield 19greatly simplifies the manufacturing process since its one-piececonstruction requires only simple bends and cuts for fabrication, andalso by reason of the use of the cut tabs formed directl from the metalstrip 20. Note that the inventive shie d uses only three tabs, whilemultipiece shields use superfluous tabs, e.g., the three-piece shielduses six tabs, all of which must be spot welded. it is evident thatinserting the magnetic shield into the convergence cup and welding it inposition is much simpler with the onepiece shield 19 than with athree-piece or two-piece shield.

Referring to the embodiment of the invention shown in FIGS. 4 and 5, inwhich like parts are designated by like reference numerals, to eliminatethe openings 26 from the flange 12, the shield 19 is sized so that thetabs 21 and 23 extend circumferentially of the inner surface of theflange. Spot welding the tabs then secures the shield at its desiredposition in the convergence cup.

I claim:

1. A convergence cup for use in color kinescopes comprising a cup-likebody having a circular base and a cylindrical flange extendingperpendicularly from the perimeter of the base, three circumferentiallyspacedapart pairs of pole pieces radially extending inwardly through theflange, three apertures in the circular base adapted to pass electronbeams between the pole pieces, and a one-piece shield dividing thevolume within the cylindrical flange into three sections to magneticallyseparate the pairs of pole pieces, the onepiece shield being formed froma single flat magnetic metal strip bent 180 along a lateral lineintermediate its ends and having the two resulting legs bent outwardlyalong lateral lines intermediate their ends to provide the Y-shapedshield, and means fastening the shield to the flange comprising two tabsrespectively extending from the ends of the legs and a third tab cutfrom the strip and extending from the bend intermediate the metal stripends, each of the tabs being oriented to extend through a slot providedin the flange and extend circumferentially of the cylindrical flange onthe exterior surface thereof, and each of the tabs being welded to saidexterior surface.

2. A convergence cup for use in color kinescopes comprising a cup-likebody having a circular base and a cylindrical flange extendingperpendicularly from the perimeter of the base, three circumferentiallyspacedapart pairs of pole pieces radially extending inwardly through theflange, three apertures in the circular base adapted to pass electronbeams between the pole pieces, and a one-piece shield dividing thevolume within the cylindrical flange into three sections to magneticallyseparate the pairs of pole pieces, the onepiece shield being formed froma single flat magnetic metal strip bent 180 along a lateral lineintermediate its ends and having the two resulting legs bent 120outwardly along lateral lines intermediate their ends to provide theY-shaped shield, and means fastening the shield to the flange comprisingtwo tabs respectively extending from the ends of the legs and a thirdtab cut from the strip and extending from the 180 bend intermediate themetal strip ends, each of the tabs being oriented to extendcircumferentially of the cylindrical flange on the interior surfacethereof and being welded to said interior surface.

1. A convergence cup for use in color kinescopes comprising a cup-likebody having a circular base and a cylindrical flange extendingperpendicularly from the perimeter of the base, three circumferentiallyspaced-apart pairs of pole pieces radially extending inwardly throughthe flange, three apeRtures in the circular base adapted to passelectron beams between the pole pieces, and a one-piece shield dividingthe volume within the cylindrical flange into three sections tomagnetically separate the pairs of pole pieces, the one-piece shieldbeing formed from a single flat magnetic metal strip bent 180* along alateral line intermediate its ends and having the two resulting legsbent 120* outwardly along lateral lines intermediate their ends toprovide the Y-shaped shield, and means fastening the shield to theflange comprising two tabs respectively extending from the ends of thelegs and a third tab cut from the strip and extending from the 180* bendintermediate the metal strip ends, each of the tabs being oriented toextend through a slot provided in the flange and extendcircumferentially of the cylindrical flange on the exterior surfacethereof, and each of the tabs being welded to said exterior surface. 2.A convergence cup for use in color kinescopes comprising a cup-like bodyhaving a circular base and a cylindrical flange extendingperpendicularly from the perimeter of the base, three circumferentiallyspaced-apart pairs of pole pieces radially extending inwardly throughthe flange, three apertures in the circular base adapted to passelectron beams between the pole pieces, and a one-piece shield dividingthe volume within the cylindrical flange into three sections tomagnetically separate the pairs of pole pieces, the one-piece shieldbeing formed from a single flat magnetic metal strip bent 180* along alateral line intermediate its ends and having the two resulting legsbent 120* outwardly along lateral lines intermediate their ends toprovide the Y-shaped shield, and means fastening the shield to theflange comprising two tabs respectively extending from the ends of thelegs and a third tab cut from the strip and extending from the 180* bendintermediate the metal strip ends, each of the tabs being oriented toextend circumferentially of the cylindrical flange on the interiorsurface thereof and being welded to said interior surface.